Cisc And Risc Processor Technologies Essay Research

Cisc And Risc Processor Technologies Essay, Research Paper

TABLE OF CONTENTS

1. Abstract 2

2. Introduction 3

3. CISC Technology 4

3.1 Characteristics 4

3.2 The Advantages of CISC 5

3.3 The Disadvantages of CISC 5

4. RISC Technology 6

4.1 Characteristics 6

4.2 The Advantages of RISC 7

4.3 The Disadvantages of RISC 8

5. Conclusion 9

6. References 10

1.Abstract

This report describes the CISC and RISC technologies. Describes the characteristics of each of these technologies. Also Advantages and disadvantages of both technologies are described. So the reader will be able to recognize and compare both technologies.

This report describes the “CISC” style of computer processor architecture. Which is the most commonly used style today. By reading this report you will be able to define the term CISC. Be able to list the characteristics of a CISC instruction set and also the decisions and philosophies which led to the development for this technology.

Also this report describes the RISC style of computer processor architecture. Which is replacing CISC in some uses. Define the term RISC. Describe the characteristics of RISC technology. And also point the advantages and disadvantages of using this technology.

At the end of this report you will also be able to describe the major differences between a CISC instruction set and a RISC instruction set and list some key advantages and disadvantages of RISC as compared to CISC

2. Introduction

Speeding up a computer system involves many different strategies. By speeding up the input and output devices in different peripherals. But the most fruitful place to speed up the system is by designing a faster processor. This report will explain “CISC” and “RISC” technologies and show how computer designers have tried to do speed up processors by implementing these tow technologies.

CISC technology was not known as a processor technology back in time. It was just the way that manufactures designed processors. So the Term CISC was define just when the RISC philosophy was adopted.

In the mid-1970 s advances in technology began to reduce the difference in speed between main memory and processor chips. As memory speed increased, and high level languages displaces assembly language the major reasons for Complex Instruction Set Computers began to disappear and computer designers began to look in at ways computer performance could be optimized beyond just making faster hardware. That is when RISC technology started to emergence.

3. CISC Technology

CISC as defined by [WISCISC1] stands for Complex Instruction Set Computer, is a philosophy for designing chips that are easy to program and which make efficient use of memory. Each instruction in a CISC instruction set might perform a series of operations inside the processor. This reduces the number of instructions required to implement a given program, and allows the programmer to learn a small but flexible set of instructions.

Since the earliest machines were programmed in assembly language and memory was slow and expensive, the CISC philosophy made sense, and was commonly implemented in large computer systems.

Most common microprocessor designs including the Intel 80×86 and Motorola 68K series also follow the CISC philosophy.

As we shall see, recent changes in software and hardware technology have forced a re-examination of CISC.

3.1 Characteristics

The three decisions that led to the CISC philosophy, which drove all computer designs until the late 1980s, and is still in major use today.

Microcode

Build of rich instruction sets

Build of high-level instruction sets

3.2 The Advantages of CISC

At the time of their initial development, CISC machines used available technologies to optimize computer performance.

Microprogramming is as easy as assembly language to implement, and much less expensive than hardwiring a control unit.

The ease of micro coding new instructions allowed designers to make CISC machines upwardly compatible: a new computer could run the same programs as earlier computers because the new computer would contain a superset of the instructions of the earlier computers.

As each instruction became more capable, fewer instructions could be used to implement a given task. This made more efficient use of the relatively slow main memory.

Because micro program instruction sets can be written to match the constructs of high-level languages, the compiler does not have to be complicated.

3.3 The Disadvantages of CISC

Still, designers soon realized that the CISC philosophy had its own problems, including:

Earlier generations of a processor family generally were contained as a subset in every new version so instruction set & chip hardware become more complex with each generation of computers.

So that as many instructions as possible could be stored in memory with the least possible wasted space, individual instructions could be of almost any length. This means that different instructions will take different amounts of clock time to execute, slowing down the overall performance of the machine.

Many speci

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